Method for producing hydrogen

ABSTRACT

A method for controlling the purity of hydrogen in a reforming apparatus is described where in the apparatus includes a fuel processor, a purification unit and a system controller. The controller determines a calculated flow of reformate from the fuel processor and operates the purification unit based on the calculated flow. The calculated flow is derived from a process model of the fuel processor and known feed(s) to the fuel processor. The calculated flow of reformate is used to control the flow of reformate to adsorbent beds within the purification unit and can be used to control other materials flows within the apparatus. Means for reducing fluctuations in the pressure and/or flow rate of reformate flowing from the fuel processor to the purification unit are also disclosed. The purity of the hydrogen produced can be maintained by adjusting the operation of the purification unit in response to changes in reformate composition, pressure and/or flow rate.

The present invention is a divisional application of U.S. Ser. No.11/015,358, filed Dec. 17, 2004, now U.S. Pat. No. 7,402,287 thecomplete disclosure of which, is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of hydrogenproduction. The apparatus and methods of the present invention producehydrogen by removing impurities from an intermediate reformatecomprising hydrogen and one or more impurities through selectiveadsorption. The selective adsorption can be carried out in a pressureswing adsorption unit wherein the adsorption period is controlled andadjusted to achieve greater product purity. More specifically, thepresent invention relates to the integration and operation of a pressureswing adsorbent unit with a fuel processing unit to produce hydrogen.

BACKGROUND OF THE INVENTION

Hydrogen is utilized in a wide variety of industries ranging fromaerospace to food production to oil and gas production and refining.Hydrogen is used in these industries as a propellant, an atmosphere, acarrier gas, a diluent gas, a fuel component for combustion reactions, afuel for fuel cells, as well as a reducing agent in numerous chemicalreactions and processes. In addition, hydrogen is being considered as analternative fuel for power generation because it is renewable, abundant,efficient, and unlike other alternatives, produces zero emissions. Whilethere is wide-spread consumption of hydrogen and great potential foreven more, a disadvantage which inhibits further increases in hydrogenconsumption is the absence of an infrastructure that can providegeneration, storage and widespread distribution of hydrogen.

One way to overcome this difficulty is through distributed generation ofhydrogen, such as through the use of fuel processors to converthydrocarbon-based fuels to hydrogen-rich reformate. Fuel reformingprocesses, such as steam reforming, partial oxidation, and autothermalreforming, can be used to convert hydrocarbon-based fuels such asnatural gas, LPG, gasoline, and diesel, into hydrogen-rich reformate ata site where hydrogen is needed. However, in addition to the desiredhydrogen product, fuel reformers typically produce undesirableimpurities that reduce the value of the reformed product. For instance,in a conventional steam reforming process, a hydrocarbon feed, such asmethane, natural gas, propane, gasoline, naphtha, or diesel, isvaporized, mixed with steam, and passed over a steam reforming catalyst.The majority of the hydrocarbon feed is converted to a reformate mixtureof hydrogen and impurities such as carbon monoxide and carbon dioxide.To reduce the carbon monoxide content, the reformate is typicallysubjected to a water-gas shift reaction wherein the carbon monoxide isreacted with steam to form carbon dioxide and hydrogen. After the shiftreaction(s), additional purification steps may be utilized to bring thehydrogen purity to acceptable levels. These purification steps caninclude, but are not limited to, methanation, selective oxidationreactions, membrane separation techniques, and selective adsorption suchas in temperature swing and/or pressure swing adsorption processes.

Gas separation by pressure swing adsorption (PSA) is achieved bycoordinated pressure cycling over an adsorbent bed that preferentiallyadsorbs a more readily adsorbed component relative to a less readilyadsorbed component of a mixture. In a conventional PSA device, two ormore adsorbent beds are connected in alternating sequence by directionalvalving to pressure sources and sinks for establishing the changes ofworking pressure and flow direction. In another conventional PSA device,flows to and from adsorbent beds are controlled by a rotary distributionvalve that is rotated to cycle the adsorbent beds through adsorption andregeneration phases. For instance, the separation of oxygen from air isa known application of such conventional PSA devices. However, in suchapplications the composition of the gas mixture, its pressure and/orflow rate are typically fixed and known. In contrast, the integration ofa PSA device to a fuel processor that produces a product of varyingcomposition, pressure and/or flow rate imposes challenges to theefficient operation of such a system.

SUMMARY OF THE INVENTION

In an aspect of the present invention an apparatus for producinghydrogen is provided. An apparatus of the present invention includes afuel processor capable of producing a flow of intermediate reformatecomprising hydrogen and an impurity. The intermediate reformate can havea variable composition, pressure and/or flow rate. The apparatusincludes a purification unit disposed downstream of the fuel processorcapable of removing impurity from the flow of intermediate reformate toproduce a flow of hydrogen-enriched reformate. A controller is providedthat is capable of determining a calculated flow of intermediatereformate to be produced by the fuel processor from a process model ofthe fuel processor. The controller is capable of operating thepurification unit in response to the calculated flow of intermediatereformate.

In a process aspect of the present invention, a method for producing ahydrogen-enriched reformate is provided. The method includes the step ofproducing a flow of intermediate reformate comprising hydrogen and animpurity in a fuel processor. The intermediate reformate produced canhave a variable composition, pressure and/or flow rate. Impurity isremoved from the intermediate reformate to produce a flow ofhydrogen-enriched reformate. A calculated flow of intermediate reformateto be produced by the fuel processor is determined from a process modelof the fuel processor. The purification unit is operated in response tothe calculated flow of intermediate reformate. The method can optionallyinclude the steps of selecting a hydrogen-enriched reformate output anddetermining the calculated flow of intermediate reformate based on theselected hydrogen-enriched reformate output, or selecting one or morefeeds to the fuel processor and determining the calculated flow ofintermediate reformate in part from the selected feed(s).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic illustration of an embodiment of the presentinvention comprising a fuel processor and a purification unit.

FIG. 2 is a schematic illustration of an embodiment of the presentinvention comprising a fuel processor and a purification unit.

FIG. 3 is a schematic illustration of an embodiment of the presentinvention comprising a fuel processor and a purification unit.

FIG. 4 is a block diagram illustrating a process flow within a fuelprocessor capable of producing an intermediate reformate.

FIG. 5 is a block diagram of a method of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual embodiment aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The product stream from a fuel processor is typically rich in hydrogenbut can contain one or more impurities such as carbon monoxide, carbondioxide, water, steam, inert components such as nitrogen and argon,various sulfur and nitrogen-containing compounds as well as unreactedhydrocarbons. Such impurities must be removed or reduced to extremelylow levels to render the hydrogen product safe and reliable. Inaddition, product streams from fuel processors can have fluctuations incomposition, pressure and/or flow rate that can interfere with thepurification and clean-up of the product. The present invention isdirected to an apparatus and method for reducing or dampening suchfluctuations and for adjusting the operation of a purification unit soas to maintain a desired product composition.

An apparatus of the present invention for producing hydrogen includes afuel processor capable of producing a flow of intermediate reformatecomprising hydrogen and an impurity. The flow of intermediate reformatecan have fluctuations in composition, pressure and/or flow rate.Optionally, a compression unit can be disposed downstream of the fuelprocessor for receiving the flow of intermediate reformate and producinga flow of compressed intermediate reformate for delivery to apurification unit. A purification unit is provided downstream of thefuel processor for removing impurity from the flow of intermediatereformate to produce a hydrogen-enriched reformate. The purificationunit has a plurality of adsorbent beds and a valve assembly forselectively controlling the flow of intermediate reformate to one ormore of the plurality of adsorbent beds. A controller is included thatis capable of determining a calculated flow of intermediate reformate tobe produced by the fuel processor from a process model of the fuelprocessor. The controller is further capable of operating thepurification unit in response to the calculated flow of intermediatereformate.

A fuel processor suitable for use in an apparatus of the presentinvention includes a device or apparatus that is capable of producing anintermediate reformate comprising hydrogen and one or more impurities.The ultimate objective of an apparatus of the present invention is toproduce a substantially pure hydrogen product that can be used safelyand reliably in any hydrogen-consuming device or process. As such, an“impurity” in this context includes any material that has the potentialto foul, damage or otherwise interfere with the operation ofhydrogen-consuming device or process or a hydrogen-storage device. Suchimpurities typically include sulfur-containing compounds,nitrogen-containing compounds, carbon oxides, liquid water, steam,unreacted hydrocarbons, and inert gases.

In some embodiments, the fuel processor can include an oxidizer andreformer for converting a fuel to a reformate that comprises hydrogenand one or more impurities. Reformers are well known in the fuelprocessing art and can be designed to perform one or more of steamreforming, partial oxidation, and autothermal reforming among others.Although suitable fuel processors can utilize any known reformer, thefollowing illustrative description associated with FIG. 4 is adaptedfrom U.S. patent application Ser. No. 10/006,963, entitled “Compact FuelProcessor for Producing a Hydrogen Rich Gas,” filed Dec. 5, 2001, in thename of Krause, et al., and published Jul. 18, 2002 (Publication No.US2002/0094310 A1), which describes a fuel processor for performing acombination of steam reforming and autothermal reforming.

As illustrated in FIG. 4, the feed to the fuel processor can include ahydrocarbon-based fuel, oxygen, water, and mixtures of the same.Hydrocarbon-based fuels suitable for use in the processor can includenatural gas, LPG, gasoline, diesel, alcohols, and mixtures thereof.Natural gas is a preferred hydrocarbon-based fuel. Oxygen can be in theform of air, oxygen-enriched air, or substantially pure oxygen. Fuel(s)and water can be introduced as liquid and/or vapor. However, dependingon the initial phase of the feed materials and the nature of thereforming reaction(s) some degree of feed preparation may be required.For instance, it is preferred that both liquid water and fuel(s) beconverted to a gas phase, and further that reactants be pre-heated priorto their introduction into a reaction zone within the reformer. Ametering device can be used to provide automated control over the flowof each of the feeds to the fuel processor and sensors can be used toprovide feedback concerning the composition, pressure and/or flow rateof those feeds.

Block A of FIG. 4 represents a reforming step, in which, in oneparticular embodiment, two reactions, a partial oxidation (formula I,below) and a steam reforming (formula II, below), are performed toconvert the feed into a synthesis gas containing hydrogen and carbonmonoxide. Formulas I and II are exemplary reaction formulas whereinmethane is considered as the hydrocarbon:CH₄+½O₂->2H₂+CO  (I)CH₄+H₂O->3H₂+CO  (II)A higher concentration of oxygen in the feed stream favors theexothermic partial oxidation whereas a higher concentration of watervapor favors the endothermic steam reforming reaction. Therefore, theratios of oxygen to hydrocarbon and water to hydrocarbon as well as thereaction temperature are characterizing parameters that affect hydrogenyield. The reaction temperature of reforming step A can range from about550° C. to about 900° C., depending on the feed conditions and thecatalyst. Examples of partial oxidation and steam reforming catalystsare well known in the fuel reforming art and are not described indetail.

Block B represents a cooling step wherein the synthesis gas stream fromreforming step A is cooled to a temperature of from about 200° C. toabout 600° C., and preferably from about 375° C. to about 425° C., toprepare the synthesis gas for process step C (discussed below). Thiscooling may be achieved with heat sinks, heat pipes, heat exchangers orthe like depending upon the design specifications and the extent towhich heat is to be recovered/recycled from the synthesis gas. Coolingof the synthesis gas can also be achieved by other means known in theart, e.g. injection of a lower temperature steam into the synthesis gasstream.

Block C represents a desulphurization step. An impurity of many fuels issulfur, which is commonly converted to hydrogen sulfide during reformingstep A. Desulfurization preferably utilizes zinc oxide and/or othermaterial(s) capable of absorbing and converting the hydrogen sulfide,with or without a support (e.g., monolith, extrudate, pellet, etc.).Desulphurization can be accomplished by converting the hydrogen sulfideto zinc sulfide in accordance with the following reaction formula III:H₂S+ZnO→H₂O+ZnS  (III)Desulfurization is preferably carried out at a temperature of from about300° C. to about 500° C., and more preferably from about 375° C. toabout 425° C.

The desulfurized process stream may then be sent to a mixing step Dwherein water received from a water subsystem is optionally added. Theaddition of water serves the dual purposes of lowering the temperatureof the process stream and of supplying additional water for use in thewater gas shift reaction to follow. The water vapor and other streamcomponents are mixed by being passed through a stage of inert materialssuch as ceramic beads or other similar materials that effectively mixand/or assist in the vaporization of water. Alternatively, additionalwater can be introduced prior to reforming step A and the mixing stepcan be repositioned or eliminated. Where the process stream is to besubjected to a selective oxidation, a mixing step may also be utilizedto mix an oxidant with the process stream prior to oxidation.

Block E represents a water gas shift reaction step that converts carbonmonoxide to carbon dioxide in accordance with formula IV:H₂O+CO→H₂+CO₂  (IV)Generally, the water gas shift reaction can take place at temperaturesranging from 150° C. to 600° C. depending on the catalyst. Under suchconditions, much of the carbon monoxide in the gas stream is convertedto carbon dioxide. Where the hydrogen-enriched reformate is to be usedas a fuel for fuel cells, the concentration of carbon monoxide needs tobe lowered to a level that can be tolerated by fuel cell catalyst(s),typically below about 50 ppm. Examples of water gas shift catalysts,both low and high temperature catalysts, are well known in the fuelreforming art and are not set forth in detail herein.

Block F represents a cooling step that can be performed in an inertstage or otherwise to reduce the temperature of the process stream to atemperature preferably in the range of from about 90° C. to about 150°C. When the cooling step F is to be followed by a selective orpreferential oxidation step, oxygen from an air subsystem can also beadded to the process stream.

Block G represents an optional selective or preferential oxidation stepwherein much of the remaining carbon monoxide in the process stream isconverted to carbon dioxide. Although this oxidation is carried out inthe presence of a catalyst having activity for oxidizing carbonmonoxide, two reactions typically occur, namely, a desirable oxidationof carbon monoxide (formula V) and an undesirable oxidation of hydrogen(formula VI).CO+½O₂→CO₂  (V)H₂+½O₂→H₂O  (VI)Since both reactions produce heat and because the preferred oxidation ofcarbon monoxide is favored by low temperatures, it may be advantageousto optionally include a cooling element such as a cooling coil within anoxidation reaction zone. The oxidation reaction temperature ispreferably kept in the range of from about 90° C. to about 150° C.Because an apparatus of the present invention comprises a purificationunit such as a pressure swing adsorption unit for separating hydrogenfrom impurities, the use of selective oxidation step G may be omitted.

As noted herein, the intermediate reformate produced by a fuel processoris rich in hydrogen but can contain one or more impurities, and thus,must be subjected to purification or clean-up to remove or reduce suchimpurities to extremely low levels. Depending on the nature of thepurification technique to be used, the pressure of the intermediatereformate may need to be increased prior to delivery to the purificationunit. Therefore, an apparatus of the present invention can optionallyinclude a compression unit downstream of the fuel processor forreceiving a flow of intermediate reformate and producing a flow ofcompressed intermediate reformate. In some embodiments, such as wherethe hydrogen-enriched reformate exiting the purification unit isdestined for a storage at elevated pressure, a second compression unitcan optionally be disposed intermediate the purification unit and astorage unit for increasing the pressure of the hydrogen-enrichedreformate to the appropriate level.

Compression units are known in the art for compressing mixtures of gasescontaining hydrogen prior to subjecting the mixtures to separationtechniques and/or storage. A more detailed description of suchcompression technologies can be found in chemical engineering referencessuch as Perry's Chemical Engineers' Handbook, 4^(th) Ed. (McGraw-Hill,©1963), and in the patent literature such as in U.S. Pat. No. 4,690,695issued Sep. 1, 1987 to Doshi; U.S. Pat. No. 6,488,747 issued Dec. 3,2002 to Keefer et al.; and U.S. Application Publication No. US2003/0175564 A1 published Sep. 18, 2003 by Mitlitsky et al., thedescriptions of which are incorporated by reference. While thecompression unit need not be described in exacting detail, it should berecognized that a suitable compression unit can comprise a compressordriven by a fixed or variable speed motor in a single stage or two ormore compressors in a multi-stage compression unit. Further, suitablecompression units can include axial, centrifugal, reciprocating,rotary-type compressors and combinations of the same.

The pressures that the compression unit should be capable of imposing ona fluid will depend on the pressure requirements of the unit for whichcompression is needed. In the case of a purification unit comprising apressure swing adsorption unit (“PSA”), the pressure required of theflow of intermediate reformate to the PSA can vary between about 1 psigand about 600 psig. Where compression is needed to facilitate storage ofthe hydrogen-enriched reformate, the required pressure of thehydrogen-enriched reformate can vary from just above zero to more than10,000 psig. One skilled in the art will appreciate that the selectionof a suitable compression unit will be based on such factors as thecomposition of the intermediate reformate, its flow rate, pressure andtemperature, the pressure requirements of the downstream unit(s), aswell as factors such as the compression unit's power consumption,serviceability and cost.

In an embodiment wherein the purification unit comprises a pressureswing adsorption unit, the flow of intermediate reformate to a pluralityof adsorbent beds within the PSA and the adsorption period during whichimpurities are adsorbed from a flow of intermediate reformate throughthe adsorbent beds are controlled in a manner that is independent of thespeed of a compressor(s). More specifically, where the purification unitcomprises a rotary-type PSA having a rotary distribution valve forcontrolling the material flows to the adsorbent beds, the rotarydistribution valve is preferably operated independently of the speed ofa compressor(s). In such embodiments, the compression unit preferablycomprises a fixed speed compressor.

In embodiments where the compression unit comprises a compressor drivenby a fixed speed motor or an induction motor, care should be takenduring start-up when the compressor is first energized to ensure thatsufficient fluid is present at the inlet of the compressor to preventthe formation of a vacuum. Similar care should also be exercised duringshut-down and during transients of the fuel processor such as prior toresuming hydrogen production from stand-by status. As an alternative toassuring the presence of sufficient fluid, the speed of the compressormotor can be regulated by adjusting the power applied to the compressionunit and the compressor motor. Suitable means for regulating the powercan include a variable frequency drive for adjusting the line frequencyapplied to the motor, a soft start device for varying the voltageapplied to the motor, and other means known in the art for regulatingthe power applied to the motor.

As noted herein, the composition of intermediate reformate from the fuelprocessor can exhibit fluctuations or variations in pressure and/or flowrate. Thus, an apparatus of the present invention can optionally includemeans for reducing or eliminating such fluctuations before they reachthe downstream purification unit. As used herein, “reducing fluctuationsin pressure and/or flow rate” is intended to refer to reductions ineither the size or number of fluctuations in the pressure and/or flowrate of the intermediate reformate that is destined for the purificationunit. Moreover, such means can also be employed to prevent the formationof a vacuum at the inlet of the compression unit within the line(s)carrying intermediate reformate to the compression unit.

Means for reducing fluctuations in the intermediate reformate cancomprise a buffer disposed intermediate the fuel processor and thepurification unit. Although such a buffer could be disposed at anylocation intermediate the fuel processor and the purification unit, itis preferably disposed upstream from a compression unit when present sothat a more uniform flow of intermediate reformate is provided to aninlet of the compression unit. Those skilled in the art will appreciatethat such a buffer will have sufficient volume to receive a variableflow of intermediate reformate from the fuel processor while releasing amore uniform flow to the purification unit. Moreover, in an embodimentwhere the buffer is disposed upstream from the compression unit, theflow of intermediate reformate from the buffer should be sufficient toprevent a vacuum from forming at the compression unit inlet during bothstart-up and steady state operations.

In embodiments where a compression unit is disposed intermediate thefuel processor and the purification unit, the means for reducingfluctuations in the pressure and/or flow rate of the intermediatereformate can comprise a conduit for providing a controlled flow of asupplemental fluid to an inlet of a compression unit. The supplementalfluid can include a compressed flow of intermediate reformate derivedfrom an outlet of the compression unit, a hydrogen-enriched reformatederived from the purification unit, or some mixture thereof. The conduithas an outlet that directs the supplemental fluid into a line carryingintermediate reformate from the fuel processor to the compression unit.The number and location of conduit inlets are determined by thecomposition of the supplemental fluid. Where the supplemental fluidincludes a compressed intermediate reformate, the conduit has an inletintermediate the compression unit and the purification unit. Where thesupplemental fluid includes a hydrogen-enriched reformate, the conduithas an inlet downstream from an outlet of the purification unit. In suchan embodiment, the purification unit can include a first outlet fordirecting a hydrogen-enriched reformate and a second outlet fordirecting a hydrogen-depleted product out of the purification unit withthe inlet of the conduit in fluid communication with the first outlet ofthe purification unit. Moreover, the conduit can have a variable-openingvalve for controlling the flow of supplemental fluid therethrough. Thevariable-opening valve can be operated in response to the calculatedflow of intermediate reformate, or when a sensor is present for sensingfluid(s) flowing from the fuel processor, e.g. intermediate reformate,supplemental fluid(s) etc., the variable-opening valve can be operatedin response to sensed data.

An apparatus of the present invention includes a purification unitdisposed downstream of the fuel processor that receives a flow ofintermediate reformate and produces a flow of hydrogen-enrichedreformate by removing impurity therefrom. Hydrogen can be separated fromthe impurities in the intermediate reformate using a variety oftechnologies. By way of example, a number of purification processesseparate hydrogen from impurities through selective adsorption bypassing the hydrogen-containing stream under pressure through a columnor bed of adsorbent material. Selective adsorption can be performed withadsorptive materials that adsorb hydrogen and allow a hydrogen-depletedstream to pass or with materials that adsorb impurity and allow ahydrogen-enriched stream to pass. In either case, it is highly preferredthat the adsorbent materials be capable of regeneration throughtechniques such as pressure swing, temperature swing and the like. Insome embodiments, purification is carried out in a PSA unit havingadsorptive materials that selectively adsorb impurities and allow ahydrogen-enriched reformate to pass.

The purification unit comprises a plurality of adsorbent beds, each ofwhich is capable of removing one or more impurities from an intermediatereformate flowing through the bed. An adsorbent bed can include a vesselfor housing adsorbent material(s). The adsorbent materials can take avariety of forms including packed beds of agglomerates, pellets,particles, and/or beads, monolithic structures, as well as varioussupports coated with adsorbent materials, e.g. coated sheets. In someembodiments, the adsorbent materials are provided as a packed bed havingmultiple layers of different adsorbent materials and/or mixtures ofdifferent adsorbent materials. In other embodiments, the adsorbent bedcomprises a coated monolith or other structure configured to providefluid pathways through the bed. Adsorbent materials suitable for use inthe plurality of beds of the purification unit will depend on thematerials to be adsorbed and removed from the process stream. By way ofexample, adsorbent materials known for use in removing water vapor,carbon dioxide and hydrocarbons can include alumina gels, activatedcarbon, silica gels and zeolites Moreover, zeolites such as low silica Xzeolite and calcium or strontium exchanged chabazite are known forremoving carbon monoxide and nitrogen.

The terminology “adsorption period” is used herein to refer to theperiod or the length of time that a flow of intermediate or compressedintermediate reformate is directed through an adsorbent bed for purposesof removing impurity. At the conclusion of an adsorption period, theflow of intermediate reformate through a first adsorbent bed isinterrupted and the flow is re-directed to a second adsorbent bed so asto continue the removal of impurity and the production ofhydrogen-enriched reformate while enabling the first adsorbent bed to beregenerated. It is envisioned that two or more adsorption beds will beoperated in an adsorption phase while the other adsorption beds areundergoing various stages of regeneration. Moreover, suitablepurification units will include those that are capable of adjusting andmanipulating the adsorption period so as to compensate for fluctuationsin the composition, pressure and/or flow rate of an intermediatereformate that is fed to the unit. The manner in which the adsorptionperiod can be adjusted for purposes of achieving a hydrogen-enrichedreformate depends on the type and structure of the purification unitselected.

In some embodiments, the purification unit comprises a pressure swingadsorption unit. Suitable PSA units include those known in the art forseparating hydrogen from a process stream, such as are described in U.S.Pat. No. 4,238,204 issued Dec. 9, 1980 to Perry; U.S. Pat. No. 4,690,695issued Sep. 1, 1987 to Doshi; U.S. Pat. No. 5,256,174 issued Oct. 26,1993 to Kai et al.; U.S. Pat. No. 5,435,836 issued Jul. 25, 1995 toAnand et al.; U.S. Pat. No. 5,669,960 issued Sep. 23, 1997 to Couche;U.S. Pat. No. 5,753,010 issued May 19, 1998 to Sircar et al.; and U.S.Pat. No. 6,471,744 issued Oct. 29, 2002 to Hill, the descriptions ofwhich are incorporated herein by reference. In some embodiments, thepurification unit will comprise a compact PSA. Suitable compact PSAs caninclude a rotary-type PSA such as are described in U.S. Pat. No.6,063,161 issued May 16, 2000 to Keefer et al. and in U.S. Pat. No.6,406,523 issued Jun. 18, 2002 to Connor et al., the descriptions ofwhich are incorporated herein by reference. Compact PSAs having rotaryelements are commercially available from Questair Technologies, Inc. ofBurnaby, Canada. Questair's rotary-type PSA, model series number H3200,were used in the development of the present invention.

The purification unit optionally but preferably includes a valveassembly that is capable of selectively controlling the flow of theintermediate reformate to one or more of the plurality of adsorbentbeds. The valve assembly can comprise single or multiple valves havingfixed or variable openings that are opened and closed to controlmaterial flows to the adsorbent-beds. The valve assembly is capable ofproviding control over the flow of intermediate reformate to theadsorbent beds by selectively controlling which adsorbent bed(s) receivea flow of intermediate reformate and by controlling the sequence inwhich different materials are directed through an adsorbent bed. Assuch, the configuration of the valve assembly provides control over boththe adsorption period and regeneration phases of each adsorbent bed.Depending on the nature of the adsorbent materials within the beds,regeneration can comprise imposing pressure and/or temperature swings,directing various materials through the bed and the like.

In an embodiment where the purification unit comprises a rotary-typePSA, rotation is created between the valve assembly and the plurality ofadsorbent beds or inlets to the adsorbent beds so as to cycle each ofthe plurality of beds through adsorption-regeneration cycles. Valveassemblies for use in rotary-type PSAs are described in U.S. Pat. No.4,925,464 issued May 15, 1990 to Rabenau et al.; U.S. Pat. No. 5,593,478issued Jan. 14, 1997 to Hill et al.; U.S. Pat. No. 5,807,423 issued Sep.15, 1998 to Lemcoff et al.; U.S. Pat. No. 6,056,804 issued May 2, 2000to Keefer et al.; U.S. Pat. No. 6,372,026 B1 issued Apr. 16, 2002 toTakemasa et al.; U.S. Pat. No. 6,451,095 issued Sep. 17, 2002 to Keeferet al.; and U.S. Pat. No. 6,712,087 issued Mar. 30, 2004 to Hill et al.,the descriptions of which are incorporated by reference. Rotationbetween the valve assembly and the adsorbent beds is preferably createdby a variable-speed motor. Whereas the valve assembly controls thesequence of operations for each phase of the plurality of beds, thevariable speed motor controls the length of each of those operations andthe frequency at which the operations change. By adjusting the speed ofsuch a motor, the adsorption period for each of the plurality of bedscan be increased or decreased. Moreover, such changes in speed alter thefrequency at which the flow of intermediate reformate is switched from afirst adsorbent bed to a second adsorbent bed.

An apparatus of the present invention can optionally include a productsensor disposed downstream from the purification unit that is capable ofsensing the hydrogen-enriched reformate and/or a hydrogen-depletedproduct and generating sensed product data therefrom. The sensed productdata generated by the product sensor can be relayed or communicated tothe controller, described below, for use in operating the purificationunit. Preferably, the product sensor is disposed downstream andproximate to an outlet of the purification unit so that changes in thehydrogen-enriched reformate and/or the hydrogen-depleted reformate aredetected quickly and compensating action can be taken. Where an optionaltank is disposed downstream of the purification unit for receiving andstoring a hydrogen-enriched reformate, the product sensor is disposedupstream from the tank so that off-specification reformate can bedetected and diverted before it is received by the tank.

Sensed product data can comprise one or more of temperature, pressure,density, flow rate and compositional data. The product sensor preferablycomprises a gas sensor. The type of sensor selected is determined by thenature of the data that needed. In some embodiments, the product sensorcan comprise a compositional-type sensor for determining theconcentration of a component within the hydrogen-enriched reformateand/or the hydrogen-depleted reformate. For instance, sensors fordetecting the presence or concentration of carbon monoxide, carbondioxide, hydrocarbons, water, sulfur-containing compounds, andnitrogen-containing compounds are commercially available. In anembodiment where the product sensor comprises a sensor for sensingcompositional data, the sensor is preferably not suitable for sensingthe concentration of free oxygen in the hydrogen-enriched reformateand/or the hydrogen-depleted reformate.

In an embodiment where data relating to the concentration of hydrogen inthe hydrogen-enriched reformate is needed, the sensor can comprise asensor capable of directly sensing the hydrogen concentration, or one ormore sensors capable of sensing data from which the hydrogenconcentration may be determined. A description of a method and apparatusfor indirectly determining the hydrogen concentration of a reformate fedto a fuel cell can be found in U.S. Pat. No. 6,770,391 B2, issued Aug.3, 2004 to Nelson et al., the disclosure of which is incorporated hereinby reference. The concentration of hydrogen in the hydrogen-enrichedreformate exiting the purification unit should be greater than about99.96%, preferably greater than about 99.97%, and more preferablygreater than about 99.98% by vol. When the sensed product data relayedto the controller indicates that the concentration of hydrogen isdecreasing, the purification unit can increase the frequency at whichthe flow of intermediate reformate is directed from one adsorbent bed tothe next. More specifically, where the purification unit is arotary-type PSA unit having a variable-speed motor, the speed of thevariable-speed motor can be increased to shorten the adsorption period.Similarly, where the sensed product data indicates that the pressureand/or flow-rate of the hydrogen-enriched reformate is increasing, thespeed of the variable-speed motor can be increased to shorten theadsorption period and maintain a desired concentration of hydrogen inthe hydrogen-enriched reformate.

As noted above, an apparatus of the present invention includes a systemcontroller for monitoring and controlling the operation of the fuelprocessor and purification unit. As described below, the controller iscapable of determining a calculated flow of intermediate reformate to beproduced by the fuel processor and of operating the purification unit inresponse to the calculated flow of intermediate product.

The purification unit, when in the form of a pressure swing adsorptionunit, can deliver a hydrogen-enriched reformate at constant compositionprovided that the flow rate of the intermediate reformate, the pressure,and the cycle times of the PSA, e.g. adsorption, desorption, pressureequalization, repressurization, blowdown, purge sequences etc.,cumulatively referred to as “cycle times”, all remain constant. If anyof these parameters should change, the composition of thehydrogen-enriched reformate will also change. Because of changes indemand and other factors, the flow of intermediate product from the fuelprocessor to the PSA will vary from time to time. Therefore, at a givenpressure, the operation of the PSA may need to be adjusted in responseto changes in the flow of intermediate reformate in order to maintainthe composition of the hydrogen-enriched reformate. Operation of thepurification unit to maintain a constant composition requiresessentially “real-time” knowledge of the flow rate and composition ofthe flow of intermediate reformate from the fuel processor. However,measurement of the flow of intermediate reformate can be difficult andrequire expensive analytical instrumentation. Further, because of longlag times, actual measurements may not provide reliable or usable data.

In an apparatus and method of the present invention, the technique usedto control the operation of the purification unit is based on apredicted or calculated flow of intermediate reformate to be produced bythe fuel processor. This calculated flow of intermediate reformate isdetermined by the controller from a process model of the fuel processor.The process model is initially developed from the chemical reactionsthat are performed on the feeds and process streams within the fuelprocessor. Reaction conversions and compositions can be determined fromkinetic data available in the literature, and commercial modelingsoftware such as is available from Aspen Technology, Inc. of Cambridge,Mass., can be used to develop a generalized process model for the fuelprocessor. However, a suitable model must be specific to the fuelprocessor that is used to produce the intermediate reformate. Therefore,to obtain a more accurate and complete model, elements specific to thefuel processor that impact the kinetic and thermodynamic properties ofthe fuel processor should also be included. Such elements can includethe reactor materials and geometries, catalysts and other materialsdisposed in the path of the process stream, and the thermal featuresparticular to the fuel processor design. Moreover, kinetic models basedon experimental results can be used to estimate reaction conversions andcompositions to be produced by the fuel processor and to determineoptimum oxygen to carbon and steam to carbon ratios for given pressuresand temperatures. In addition, the reformer's temperature profile thatwill result from a given set of feeds at a given pressure can becalculated as the adiabatic temperature rise resulting from minimizingthe free energy of the reforming reaction(s).

When developed, the process model is capable of predicting, at steadystate and a given pressure, the composition and flow rate of theintermediate product that is to be produced from a known feed to thefuel processor. Similarly, where the intermediate reformate is to have agiven composition and flow rate, the model can determine the feeds thatare needed to produce that intermediate reformate. The process modelshould also address the dynamic operations of the fuel processor, e.g.,start-up, shut-down, turndowns and other transients.

In some embodiments, the controller can also include means forcorrelating the operation of the purification unit at a given pressurewith a calculated flow of intermediate reformate that will produce ahydrogen-enriched reformate having a desired composition and/or flowrate. Such means can include a process model of the purification unitthat is capable of determining the operational settings of thepurification unit, e.g., the adsorption period or other cycle times, forproducing a given hydrogen-enriched reformate. In an alternative, suchmeans can include a set of empirical correlations determinedexperimentally that are stored, preferably in table form, for access bythe controller. Regardless of the means used, for a given pressure andcalculated flow of intermediate reformate, the means will provide thecontroller with instructions for operating the purification unit toproduce a hydrogen-enriched reformate having a selected composition. Inan embodiment where the purification unit is a rotary-type PSA having avariable speed motor, the means for correlating can include a look-uptable wherein calculated flows of intermediate reformate at variouspressures are correlated with various motor speeds that will produce ahydrogen-enriched reformate of a given composition. As a result, changesthat may occur in the composition or flow rate of the calculated flow ofintermediate reformate can be used to identify the appropriate change inmotor speed that will adjust the operation of the purification unit soas to maintain the composition of the hydrogen-enriched reformate.Moreover, such means can be used to determine the calculated flow ofintermediate reformate from a selected hydrogen-enriched reformateoutput.

In operation, an operator can select a hydrogen-enriched reformateoutput to be produced by the hydrogen producing apparatus. The selectionof this output can comprise instructing the controller to produce ahydrogen-enriched reformate of a given quality or composition at a givenflow rate. The controller can determine the calculated flow ofintermediate reformate to be produced by the fuel processor from alook-up table based on the selected hydrogen-enriched reformate output.The controller can then set and adjust the feed(s) to the fuel processorto produce a flow of intermediate reformate based on the process modeland the calculated flow of intermediate reformate. When the fuelprocessor reaches a steady state, the flow of intermediate reformate isdirected to the purification unit. The controller operates thepurification unit in response to the calculated flow of intermediatereformate to produce the hydrogen-enriched reformate. Where changesoccur in the composition and/or flow rate of the intermediate product,the controller can adjust the operation of the purification unit, e.g.,the adsorption period, to maintain the composition of thehydrogen-enriched reformate. Optionally, the controller can receivesensed product data for the hydrogen-enriched reformate that is exitingthe purification unit and adjust the operation of the purification unitto achieve the operator selected reformate composition and flow rate.

In some embodiments, the controller is implemented on a single computingsystem for controlling each facet of the operation of the apparatus thatis not under manual control. In other embodiments, the system controllercan comprise multiple computing systems, each for controlling somedesignated facet of the operation of the apparatus. The systemcontroller can be rack-mounted or implemented as a desktop personalcomputer, a workstation, a notebook or laptop computer, an embeddedprocessor, or the like. Indeed, this aspect of any given implementationis not material to the practice of the invention.

The computing system preferably includes a processor communicating withmemory storage over a bus system. The memory storage can include a harddisk and/or random access memory (“RAM”) and/or removable storage suchas a floppy magnetic disk and/or an optical disk. The memory storage isencoded with a data structure for storing acquired data, an operatingsystem, user interface software, and an application. The user interfacesoftware, in conjunction with a display, implements a user interface.The user interface can include peripheral I/O devices such as a key pador keyboard, mouse, or joystick. The processor runs under the control ofthe operating system, which may be practically any operating systemknown to the art. The application is invoked by the operating systemupon power up, reset, or both, depending on the implementation of theoperating system.

Software implemented aspects of the invention are typically encoded onsome form of program storage medium or implemented over some type oftransmission medium. The transmission medium may be twisted wire pairs,coaxial cable, optical fiber, or some other suitable transmission mediumknown to the art. Some portions of the detailed descriptions herein arepresented in terms of a software implemented process involving symbolicrepresentations of operations on data bits within a memory in acomputing system. These descriptions and representations are the meansused by those in the art to most effectively convey the substance oftheir work to others skilled in the art. The process and operationrequire physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical, magnetic,or optical signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, data, elements, symbols, instructions, characters, terms,numbers, or the like. It should be borne in mind, however, that all ofthese and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities. Furthermore, the actions and processes of an electronicdevice that manipulates and transforms data represented as physical(electronic, magnetic, or optical) quantities within some electronicdevice's storage into other data similarly represented as physicalquantities have been denoted by terms such as “processing,” “computing,”“calculating,” “comparing,” “determining,” “displaying,” and the like.

An apparatus of the present invention can also optionally include aproduct valve disposed downstream of the purification unit for use incontrolling a flow of hydrogen-enriched reformate and/orhydrogen-depleted reformate from the purification unit. In someembodiments, the product valve is a variable-opening valve. The productvalve can be operated by the controller in response to the calculatedflow of intermediate reformate. Where a product sensor is presentdownstream from the purification unit for sensing the hydrogen-enrichedreformate and/or hydrogen-depleted reformate, the product valve can beoperated at least in part in response to sensed product data. Controlover the flow of hydrogen-enriched reformate out of the purificationunit can be used to create back-pressure within the purification unit tomaintain a more stable or fixed pressure within the purification unit.Further, such control also provides additional control over the flowrate of reformate through the purification unit for purposes ofmaintaining the composition of the hydrogen-enriched reformate.

An apparatus of the present invention can optionally include a storageunit disposed downstream of the purification unit for storing ahydrogen-enriched reformate. A compression unit can optionally beincluded for producing a flow of compressed hydrogen-enriched reformatefor storage depending on the pressure requirements of the particularstorage unit selected. Moreover, a second conduit can be included thatis capable of providing a controlled flow of supplemental fluid to aninlet of the second compression unit. The second conduit preferably hasan inlet disposed intermediate the second compression unit and thestorage unit, a valve for controlling the flow of supplemental fluidthrough the conduit, and an outlet disposed intermediate an outlet ofthe purification unit and the inlet to the second compression unit.

Storage units suitable for use in an apparatus of the present inventioncan be selected from hydrogen storage devices that are known in the art.Preferably, the hydrogen storage device will comprise a storage vesselsuitable for containing the hydrogen-enriched reformate in a desiredform, including but not limited to, pressurized gas, liquefied gas orsolid. Suitable storage vessels can be portable, modular, skid mountedor fixed in place. Further, a selected storage unit preferably hassufficient storage capacity to enable the unit to deliver storedreformate to an outlet at a selected rate during periods in which thefuel processor is not operating and/or during periods of peak demandwhen the volume of reformate produced by the fuel processor must besupplemented to meet demand.

The hydrogen storage unit may comprise a high pressure vessel operablyconnected in fluid communication with a compression unit for storing acompressed product. Suitable storage units can also utilizehydrogen-fixing material(s) that can reversibly fix hydrogen.Hydrogen-fixing materials are known in the hydrogen storage art and caninclude activated carbon, carbon composites, fullerene-based materials,metal hydrides, alloys of titanium, vanadium, chromium and manganese,with or without additional elements, magnetic hydrogen-absorbingmaterial, and nanostructures formed from light elements selected fromthe second and third rows of the periodic table. Examples of vesselscontaining hydrogen-fixing material for storing compressed hydrogen aredescribed in U.S. Pat. No. 4,598,836 issued Jul. 8, 1986 to Wessel andU.S. Pat. No. 6,432,176 B1 issued Aug. 13, 2002 to Klos et al., thedisclosures of which are incorporated herein by reference. In stillother embodiments, the storage unit can comprise a liquefaction unitcapable of converting the hydrogen-rich product to a liquefied productthrough cryogenic cooling or other liquefaction techniques.

An apparatus of the present invention can optionally include one or moresensors disposed throughout the apparatus for sensing the temperature,composition, density, pressure and/or flow rate of fluids at variouslocations within the apparatus. Those skilled in the art will appreciatethat sensed data such as temperature and pressure can be used tocalculate other fluid conditions such as density using methods such asthose described in U.S. Pat. No. 6,619,336 issued Sep. 16, 2003 to Cohenet al. In addition, sensed compositional information can be used for avariety of purposes including estimating the hydrogen concentration ofthe product as is described in U.S. Pat. No. 6,770,391 B2 issued Aug. 3,2004 to Nelson et al. Sensors for sensing and monitoring the apparatusand fluid conditions of temperature, composition, pressure and flow rateare known and commercially available.

In a process aspect of the present invention, a method for producing ahydrogen-enriched reformate is provided. The method includes producing aflow of intermediate reformate that comprises hydrogen and an impurityin a fuel processor. A process for producing an intermediate reformatein a fuel processor is described in detail above. Impurity is removedfrom the intermediate reformate in a purification unit to produce ahydrogen-enriched reformate. A calculated flow of intermediate reformateto be produced by the fuel processor is determined from a process modelof the fuel processor and the purification unit is operated, at least inpart, in response to the calculated flow of intermediate reformate.

Impurity can be removed from the intermediate reformate throughselective adsorption, and in particular, through the use of a pressureswing adsorption unit as is described above. Impurity is removed bydirecting the flow of intermediate reformate through one or more of aplurality of adsorbent beds for an adsorption period. The removal ofimpurity from a flow of intermediate reformate in a pressure swingadsorption unit depends on the flow rate and composition of theintermediate reformate as well as the pressure within the purificationunit. Typically, the flow of intermediate reformate from the fuelprocessor to the adsorbent beds of the purification unit is betweenabout 150 slpm and about 370 slpm, where standard units represent 25° C.at 1 atm. The composition of the intermediate reformate can vary butwill typically include CO<1%, CH₄<2%, CO₂>15% and H₂>40%. Moreover, thepressure within the purification unit is typically between about 70 psigand about 350 psig and is preferably fixed while the purification unitis removing impurity from the reformate. When the purification unit isproperly adjusted, a hydrogen-enriched reformate having a hydrogenconcentration of at least about 99.90% by volume, can be produced at arate of between about 40 slpm and about 120 slpm.

The purification unit can be operated in response to the calculated flowof intermediate reformate by adjusting the adsorption period in responseto the calculated flow of intermediate reformate. The purification unitpreferably comprises a valve assembly capable of selectively controllingthe flow of intermediate reformate to the plurality of adsorbent bedsand a variable speed motor for creating rotation between the valveassembly and the plurality of adsorbent beds. In such an embodiment, theadsorption period can be adjusted by changing the speed of the motor.The speed of the motor for producing a hydrogen product having thedesired purity and flow rate is design specific. In the case of aQuestair H3200 series PSA, the speed of the variable speed motor ispreferably selected and adjusted within a range between about 3 to about11 rpm to achieve the composition and flow rates noted above.

Removal of impurity preferably utilizes a plurality of adsorbent beds sothat flow through a first adsorbent bed can be interrupted andre-directed through a second adsorbent bed to continue the removal ofimpurity and the production of a flow of hydrogen-enriched reformate.Further, the interruption of flow through the first adsorbent bed andits re-direction enables the first adsorbent bed to be regenerated byone or more of depressurizing, purging, heating, cooling andre-pressurizing the bed and the adsorbent materials therein.Regeneration of an adsorbent bed favors the release of adsorbedimpurities produces a flow of exhaust or a hydrogen-depleted productcomprising the previously adsorbed impurities.

As described above, a process model of the fuel processor is used todetermine a calculated flow of intermediate reformate. The calculatedflow of intermediate reformate can include the flow rate and compositionof the intermediate reformate that will be produced by the fuelprocessor. Moreover, the calculated flow of intermediate reformate canbe determined from a feed(s) to the fuel processor or determined from aselected hydrogen-enriched reformate output. Thus, the method canfurther include selecting a feed to the fuel processor for use indetermining the calculated flow of intermediate reformate. In otherembodiments, the method can further include selecting ahydrogen-enriched reformate output for use in determining the calculatedflow of intermediate reformate needed to produce the selectedhydrogen-enriched reformate output. Selection of the hydrogen-enrichedreformate output can include a composition and/or a flow rate input.

By way of example, an operator can select the hydrogen-enrichedreformate output to be produced. The selected hydrogen-enrichedreformate output is used by the controller to determine the calculatedflow of intermediate reformate to be produced by the fuel processor. Aprocess model of the purification unit or empirical correlations asdescribed above can be used to determine the calculated flow ofintermediate reformate. The process model of the fuel processor and thecalculated flow of intermediate reformate are used by the controller toset and adjust the feeds to the fuel processor to produce intermediatereformate. When the fuel processor reaches a steady state, the flow ofintermediate reformate is directed to the purification unit to producethe hydrogen-enriched reformate. The calculated flow of intermediatereformate and a look-up table can be used by the controller to set andadjust the operation of the purification unit to produce ahydrogen-enriched reformate having the desired purity and flow rate. Inother embodiments, the operator selects a feed or set of feeds to thefuel processor and the controller determines the calculated flow ofintermediate reformate therefrom. The calculated flow of intermediatereformate can then used by the controller to set and adjust other feedsto the fuel processor and the operation of the purification unit toproduce a hydrogen-enriched reformate of desired purity.

The method of the present invention further includes operating thepurification unit in response to the calculated flow of intermediatereformate. As changes occur in the flow rate or composition of theintermediate product, adjustments in the operation of the purificationunit can be made by the controller to maintain the composition of thehydrogen-enriched reformate. More specifically, the adsorption periodcan be adjusted to maintain hydrogen purity. By way of example, when thefuel processor is turned down because of decreased hydrogen demand orfor other reasons, changes in the composition and/or flow rate of theintermediate reformate occur. Such changes are reflected in changes inthe calculated flow of intermediate reformate as well. In a method ofthe present invention, the operation of the purification unit can beadjusted by increasing or decreasing the speed of the variable speedmotor to compensate for changes in the calculated flow of intermediatereformate. Changes in the speed of the variable speed motor adjust theadsorption period and maintain the composition of the hydrogen-enrichedreformate.

Depending on the requirements of a downstream purification unit, theflow of intermediate reformate can optionally be compressed to produce aflow of compressed intermediate reformate prior to removing impuritytherefrom. In such an embodiment, the intermediate reformate can becompressed in a compressor driven by a fixed or variable speed motor fordelivery to the purification unit. In a preferred embodiment, thepurification unit is operated independent of the speed of thecompressor. Where the hydrogen-enriched reformate is optionally storedin a storage unit that requires the product gas to be stored at anelevated pressure, the flow of hydrogen-enriched reformate from thepurification unit can be compressed as well.

The intermediate reformate can have fluctuations in composition,pressure and/or flow rate. These fluctuations can optionally be reducedor dampened by buffering the intermediate reformate in a buffer upstreamfrom the purification unit. In embodiments where the intermediatereformate is compressed prior to delivery to a purification unit,fluctuations of pressure and/or flow rate can be reduced by providing acontrolled flow of a supplemental fluid to an inlet of the compressionunit. The supplemental fluid can comprise compressed intermediatereformate and/or hydrogen-enriched reformate and control over the flowcan be provided by a variable opening valve. The flow of supplementalfluid to the inlet of the compression unit can be controlled in responseto the calculated flow of intermediate reformate and/or in response to asensed pressure and/or flow rate of intermediate reformate proximate theinlet of the compression unit.

The hydrogen-enriched reformate and/or a hydrogen-depleted reformate canoptionally be sensed to generate sensed product data. Thehydrogen-enriched reformate or hydrogen-depleted reformate is senseddownstream proximate the purification unit so that sensed dataindicative of changes in the hydrogen-enriched reformate composition isdetected and compensatory action can be taken quickly. The sensedproduct data can include temperature, pressure, density, flow rate,and/or compositional data. Where the hydrogen-enriched reformate isoptionally stored in a storage unit, the hydrogen-enriched reformate issensed upstream from the storage unit so that off-specificationreformate can be diverted before it is received by the storage unit.

A method of the present invention can optionally include controlling theflow of hydrogen-enriched reformate out of the purification unit. Theflow of hydrogen-enriched reformate out of the purification unit can becontrolled by a variable-opening product valve. This valve can becontrolled in response to the calculated flow of intermediate reformateand/or in response to sensed product data generated by a product sensoras described above. Control over the flow of hydrogen-enriched reformateout of the purification unit can be used to create back-pressure withinthe purification unit to maintain a more stable or fixed pressure withinthe purification unit. Further, such control also provides additionalcontrol over the flow of reformate through the purification unit forpurposes of maintaining the composition of the hydrogen-enrichedreformate.

DETAILED DESCRIPTION OF THE FIGURES

As illustrated in FIG. 1, hydrogen producing apparatus 100 includes fuelprocessor 110, purification unit 140 and controller 170. Fuel processor110 includes oxidizer 113 and reformer 111, with the fuel processingreactants delivered to the processor through feed 102. The nature of thefuel processor will determine the number and nature of feeds. Forinstance, the feed will include conduits for delivering reactants suchas fuel, oxidant, and optionally water or steam, depending on the natureof the fuel processing reaction(s) to be performed. As illustrated, fuel101, air 103 and water 105 are provided to feed 102 for delivery to thefuel processor. The reactants are converted within fuel processor 110 toa flow of intermediate reformate that includes hydrogen and one or moreimpurities. The flow of intermediate reformate from the fuel processorcan have fluctuations in pressure, flow rate and/or composition, bothduring transient and steady state operations.

The flow of intermediate reformate is directed from fuel processor 110to purification unit 140 via line 112. Purification unit 140 usesselective adsorption to remove impurities from the intermediatereformate by directing the intermediate reformate through a bed(s) ofadsorbent material(s) that preferentially adsorb impurities and allow aproduct enriched with hydrogen to flow out of the bed. As illustrated inFIG. 1, purification unit 140 is a pressure swing adsorption unit havinga plurality of adsorption beds 150 and valve assembly 145. Materialflows to each of the plurality of adsorption beds 150 is controlled byvalve assembly 145. The purification unit further comprises a variablespeed motor 141 for creating rotation between valve assembly 145 andadsorbent beds 150. The configuration of valve assembly 145 and thespeed of variable speed motor 141 determine the operational phase of anadsorbent bed and the rate at which each bed progresses through a cycleof adsorption and regeneration. During such a cycle, an adsorption bedcan receive a flow of intermediate reformate, a flow of purge gas, canbe depressurized, evacuated, heated, cooled and/or re-pressurized amongother possible operations. It should also be noted that sources andsinks for pressurization, purge gases and the like, as well as detailsconcerning valve assembly 145 have not been illustrated in FIG. 1 so asnot to obscure the invention.

During operation, the intermediate reformate is directed into thepurification unit through valve assembly 145 and flowed through one ormore of adsorbent beds 150 for an adsorption period. The length of theadsorption period is determined by the configuration of the valveassembly 145 and the speed of motor 141. During an adsorption period,impurities within the flow of intermediate reformate are adsorbed by theadsorbent materials within the bed(s) and the flow of hydrogen-enrichedreformate is directed out of the purification unit through line 142. Asnoted herein, the purity of the hydrogen-enriched reformate can dependon a number of factors including the type of adsorbent material, theconfiguration and geometries of the bed, the flow rate of intermediatereformate, as well as pressure and temperature conditions. For a givenbed and adsorbent material, the length of the adsorption period willhave a direct bearing on the purity of the hydrogen-enriched reformateand may be adjusted to manipulate the purity of the hydrogen-enrichedreformate or to compensate for fluctuations in the pressure, flow rateand/or composition of the intermediate reformate produced by fuelprocessor 110.

Controller 170 is provided for monitoring and controlling the operationof fuel processor 110 and purification unit 140. In addition, sensors(not illustrated) are provided for sensing the reactants to be deliveredto fuel processor 110. Reactant data generated by such sensors isrelayed to controller 170 as indicated by broken lines A, B and C,respectively. Controller 170 includes a process model of fuel processor110. Reactant data is input into the process model to determine acalculated flow of intermediate reformate that is expected to beproduced by fuel processor 110 from reactants 101, 103 and 105.Input/ouput device 171 is provided for selecting one or more feeds to bedelivered to the fuel processor and/or a hydrogen-enriched reformateoutput to be produced by apparatus 100 for use in determining thecalculated flow of intermediate reformate. Based on the calculated flowof intermediate reformate, which can include composition, pressureand/or flow rate data for the flow of intermediate reformate, controller170 determines the appropriate adsorption period for purification unit140. An instruction setting and/or adjusting the speed of motor 141 isrelayed to the motor, as indicated by broken line D. In this manner,controller 170 operates purification unit 140 in response to thecalculated flow of intermediate reformate and is able to adjust theadsorption period to compensate for changes in the reformate produced byfuel processor 110 that could otherwise negatively impact the purity ofthe hydrogen-enriched reformate.

FIG. 2 illustrates an embodiment 200 of the present invention whereinthe apparatus comprises fuel processor 210 having oxidizer 213 andreformer 211. Feed 202 delivers a fuel 201, oxidant 203 and water 205for reforming in the fuel processor 210. The intermediate reformateproduced in fuel processor 210 is directed to buffer 220 via line 212,and then to compression unit 230 via line 222. The flow of intermediatereformate is compressed within compression unit 230 by compressor 235prior to being directed to purification unit 240. Purification unit 240is not unlike the purification unit illustrated in FIG. 1, having aplurality of adsorbent beds 250, a valve assembly 245 and a variablespeed motor 241 for creating rotation between the adsorbent beds and thevalve assembly.

Product sensor 260 is positioned downstream of the purification unit forsensing the hydrogen-enriched reformate flowing out of the purificationunit through line 242 and generating sensed product data. The sensedproduct data can include compositional information concerning thehydrogen-enriched reformate. The sensed product data is relayed tocontroller 270 for determining if the hydrogen-enriched reformate iswithin specification limits. Moreover, the sensed product data can beused by controller 270 to determine the accuracy of the process model offuel processor 210 for determining a calculated flow of intermediatereformate, and when needed, to modify the process model so as todetermine a more accurate calculated flow of intermediate reformate.

Controller 270 monitors and controls the operation of fuel processor210, buffer 220, compression unit 230, and purification unit 240.Reactant data is relayed to controller 270 as indicated by broken linesA′, B′ and C′ for input into the process model of fuel processor 210 fordetermining a calculated flow of intermediate reformate. Sensed productdata from product sensor 260 is relayed to controller 270 as indicatedby broken line E′. Input/ouput device 271 is provided for selecting oneor more feeds to be delivered to the fuel processor and/or ahydrogen-enriched reformate output to be produced by apparatus 200 foruse in determining the calculated flow of intermediate reformate. Basedon the calculated flow of intermediate reformate and the sensed productdata, controller 170 determines the appropriate adsorption period forpurification unit 240. An instruction that sets and/or adjusts the speedof motor 241 is relayed to the motor, as indicated by broken line D′.

The embodiment 300 illustrated in FIG. 3 includes fuel processor 310,compression unit 330, purification unit 340, tank 380 and controller370. As illustrated, feed 302 delivers a fuel 301, oxidant 303 and water305 for reforming in the fuel processing unit 310. Fuel processor 310includes an oxidizer 313 wherein fuel and oxidant are pre-heated andwater is converted to steam. The fuel processor also includes areforming reactor 311 wherein the pre-heated reactants are converted toan intermediate reformate comprising hydrogen and one or moreimpurities.

As noted herein, a flow of intermediate reformate from fuel processor310 can have variations or fluctuations in composition, pressure and/orflow rate. To reduce such fluctuations, conduit 320 having inlet 321 andvariable-opening valve 323 are provided for directing a controlled flowof compressed intermediate reformate to line 312. Sensor 325 is providedupstream of compression unit 330 for sensing the pressure and/or flowrate of intermediate reformate in line 312. Sensed pressure and/or flowrate data from sensor 325 can be relayed directly to variable-openingvalve 323, as indicated by broken line I″, for use in controlling theposition of valve 323. In an alternative, the sensed data can be relayedto controller 370 for use in operating valve 323, as indicated by brokenlines H″ and G″. A flow of compressed intermediate reformate to line 312via conduit 320 serves to dampen fluctuations in the pressure and/orflow rate of the intermediate reformate delivered to the compressionunit and prevents the formation of a vacuum within line 312 that mightotherwise draw and mix atmospheric gases with the intermediatereformate.

The intermediate reformate produced in fuel processor 310 is directed tocompression unit 320 via line 312. The compression unit receives theintermediate reformate and produces a flow of compressed intermediatereformate that is directed to purification unit 330 through line 332.Purification unit 330 has a plurality of adsorbent beds 350, a valveassembly 345 and a variable speed motor 341 for creating rotationbetween the adsorbent beds and the valve assembly. The operation ofpurification unit 330 is similar to the operation of the purificationunits illustrated in FIG. 1 and FIG. 2. Product sensor 360 is positioneddownstream of the purification unit for sensing the hydrogen-enrichedreformate flowing out of the purification unit through line 342. Thesensed product data is relayed to controller 370 as indicated by brokenline B′. Product valve 365, a variable-opening valve, is disposed inline 342 for controlling the flow of hydrogen-enriched reformate out ofthe purification unit. Tank 380 is provided downstream from thepurification unit and product sensor 360 for receiving and storing thehydrogen-enriched reformate, at least temporarily, prior to dispensingor further processing.

Controller 370 monitors and controls the operation of fuel processor310, compression unit 330, and purification unit 340. Reactant data isrelayed to controller 370 as indicated by broken lines A″, B″ and C″ forinput into the process model of fuel processor 310 for determining acalculated flow of intermediate reformate. Input/ouput device 371 isprovided for selecting one or more feeds to be delivered to the fuelprocessor and/or a hydrogen-enriched reformate output to be produced byapparatus 300 for use in determining the calculated flow of intermediatereformate. Sensed product data from product sensor 360 is relayed tocontroller 370 as indicated by broken line E″. The pressure and/or flowrate of intermediate reformate as sensed by sensor 325 is relayed tocontroller 370 as indicated by broken line H″. Controller 370 controlsor operates variable opening valve 323 in response to the calculatedflow of intermediate reformate and the pressure and/or flow rate ofintermediate reformate as sensed by sensor 325. An instruction that setsand/or adjusts the opening of valve 323 is relayed to the valve, asindicated by broken line G″. Controller 370 determines the appropriateadsorption period for purification unit 340 in response to thecalculated flow of intermediate reformate and the pressure and/or flowrate of intermediate reformate as sensed by sensor 325 and/or the sensedproduct data from product sensor 360. An instruction that sets and/oradjusts the speed of motor 341 is relayed to the motor, as indicated bybroken line D″. Controller 370 controls or operates variable openingvalve 323 in response to the calculated flow of intermediate reformateand the pressure and/or flow rate of intermediate reformate as sensed bysensor 325 and/or the sensed product data from product sensor 360. Aninstruction that sets and/or adjusts the opening of valve 363 is relayedto the valve, as indicated by broken line F″.

FIG. 4 is block diagram illustrating various process steps in a fuelprocessor capable of producing a flow of intermediate reformate. Thesteps illustrated in FIG. 4 were described in detail above and are notrepeated here. FIG. 5 is a block diagram illustrated the steps of amethod for generating a hydrogen-enriched reformate from a flow ofintermediate reformate comprising hydrogen and an impurity. The steps ofthe method are described in detail above and are not repeated here.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

1. A method for producing hydrogen-enriched reformate, the methodcomprising the steps of: producing a flow of intermediate reformatecomprising hydrogen and an impurity in a fuel processor; removingimpurity from the intermediate reformate to produce a flow ofhydrogen-enriched reformate; determining a calculated flow ofintermediate reformate to be produced by the fuel processor from aprocess model of the fuel processor; and operating the purification unitin part in response to the calculated flow of intermediate reformate. 2.The method of claim 1, wherein the purification unit comprises aplurality of adsorbent beds comprising an adsorbent material capable ofselectively adsorbing the impurity, and wherein impurity is removed fromthe flow of intermediate reformate by directing the flow through one or,more of the plurality of adsorbent beds for an adsorption period.
 3. Themethod of claim 2, wherein the purification unit is operated in responseto the calculated flow of intermediate reformate by adjusting theadsorption period in response to the calculated flow of intermediatereformate.
 4. The method of claim 2, wherein the purification unitfurther comprises a valve assembly capable of selectively controllingthe flow, of intermediate reformate to one or more of the plurality ofadsorbent beds.
 5. The method of claim 3, wherein the purificationfurther comprises a variable speed motor capable of creating rotationbetween the valve assembly and the plurality of adsorbent beds, andwherein the adsorption period is adjusted by changing the speed of themotor.
 6. The method of claim 1, further comprising compressing theintermediate reformate in a compression unit to produce a flow ofcompressed intermediate reformate prior to removing impurity therefrom.7. The method of claim 6, wherein the intermediate reformate iscompressed in a compressor driven by a fixed or variable speed motor andwherein the purification unit is operated independent of the speed ofthe compressor.
 8. The method of claim 1, further comprising bufferingthe flow of intermediate reformate prior to removing impurity from theintermediate reformate.
 9. The method of claim 1, further comprisingsensing the hydrogen-enriched reformate to produce sensed product dataand operating the purification unit in response to the sensed productdata.
 10. The method of claim 1, further comprising controlling the flowof hydrogen-enriched reformate out of the purification unit in responseto the calculated flow of intermediate reformate.
 11. The method ofclaim 9, further comprising sensing the hydrogen-enriched reformate toproduce sensed product data and controlling the flow ofhydrogen-enriched reformate out of the purification unit in response tosensed product data.
 12. The method of claim 1, further comprisingselecting a hydrogen-enriched reformate output and determining thecalculated flow of intermediate reformate based on the selectedhydrogen-enriched reformate output.
 13. The method of claim 12, whereinthe calculated flow of intermediate reformate is determined from alook-up table.
 14. The method of claim 13, further comprisingcontrolling a feed to the fuel processor in response to the calculatedflow of intermediate reformate.
 15. The method of claim 1, furthercomprising selecting one or more feeds to the fuel processor and whereinthe calculated flow of intermediate reformate is determined in part fromthe selected feed(s).